Acidification of pig slurry before separation to improve slurry management on farms

Abstract

Pig slurry, rich in plant nutrients such as nitrogen (N) and phosphorus (P), is generally applied to soil as organic fertilizer. However, costs related to slurry transport may limit its utilization to fields close to the farm, leading to significant N losses, namely ammonia (NH3) emissions. Slurry acidification, to minimize NH3 emissions, is a potential solution to this problem, while solid-liquid separation leads to a solid fraction (SF) - rich in organic matter (OM) and phosphorus - and a liquid fraction (LF) rich in soluble nutrients. We hypothesized that a combination of acidification and separation could affect the quality of the resulting fractions depending on the separation technique used. After acidification, the two most common techniques for separation, centrifugation (CF) and screw-press (SP), were applied. The main characteristics of the slurry fractions in terms of nutrient concentrations and speciation as well as the potential N mineralization (PNM) were analysed. Our results show SFs with improved properties, mostly N and PNM when acidification is performed before separation with both techniques. The PNM was significantly increased in LFs from both techniques after acidification. The [Formula: see text] concentration increased in LFs from SP with acidification; therefore, slurry acidification is recommended to avoid any N losses during the separation process with SP, while CF may not require such pretreatment. Acidification could allow the use of a cheaper technique such as SP relative to CF since it prevents NH3 emissions during the separation process and leads to more equilibrated fractions in terms of nutrient composition.

Acidified Biogas Residues Improve Nutrient Uptake and Growth of Young Maize

“…We observed an increase of H2O-soluble P from 15% to 44% of TP. These results correspond well with Regueiro et al [9], who found an H2O-soluble P content of 36% in acidified pig slurry, while the dissolved P in the untreated slurry (pH 7.4) was below the detection limit. Very similar results were obtained by Pedersen et al [12] with acidified cattle slurry.…”

“…Acidification of slurry also has further effects on slurry composition. While total nutrient concentrations of phosphorous (P), calcium (Ca), and magnesium (Mg) remain the same [9], the dissolved contents of these nutrients are increased by slurry acidification [10], thereby increasing nutrient availability. Yield-increasing effects after fertilization with acidified pig slurry, as well as cattle slurry, have been shown in previous research [11,12].…”

Alternatives to sulfuric acid for slurry acidification: impact on slurry composition and ammonia emissions during storage

“…The changes in degradation pathways controlled by microorganisms observed after acidification of slurries have an effect on the slurry composition. An increase in the concentrations of soluble components in acidified slurries has been reported in previous studies (Regueiro et al, 2016) and may be pertinent during long storage periods. Therefore, it is important to understand the changes in the contents of nutrients and organic matter (OM) that occur during acidification and storage.…”

Acidified Animal Manure Products Combined with a Nitrification Inhibitor Can Serve as a Starter Fertilizer for Maize

“…Struvite and dicalcium-phosphate are abundant in animal manure. Previous studies have shown high increases in soluble phosphorus concentration when decreasing pH to 5.5 with sulfuric acid [32] and it has been attributed to struvite dissolution [33], but also to partial hydrolysis of less soluble fractions of organic P to more labile forms [34], explaining the WEP increase.…”